Allow configure credential repository.

Change-Id: I6301c401cfbd02590b770e7caac4155645bf866c
diff --git a/metadata/service/server/single.yml b/metadata/service/server/single.yml
index 5269121..d131fd7 100644
--- a/metadata/service/server/single.yml
+++ b/metadata/service/server/single.yml
@@ -30,6 +30,8 @@
         engine: cache
         expiration: 43200
         location: /etc/keystone/fernet-keys/
+      credential:
+        location: /etc/keystone/credential-keys/
       message_queue:
         engine: rabbitmq
         host: ${_param:single_address}